Worm study suggests mothers are hardwired to sacrifice health to produce future generations

By @iamkarlatecson on
A petri dish containing C. elegans nemotodes, (round worms), is prepared for examination by NASA scientists in this photo released on May 7, 2003. Reuters/NASA/Handout

Scientists have found that during stressful times, a biological mechanism channels a mother’s available energy straight to the reproductive system, protecting future offspring at the cost of the mother’s health.

While the phenomenon was observed in the worm species C. elegans, the cellular mechanisms associated with it also exist in humans, raising the possibility that they may share the trait as well, according to researchers at the University of Southern California.

When an organism is exposed to external stresses such as famine, a protein that protects cells called SKN-1 is activated. In addition to stress resistance, the activation of SKN-1 also drives the reallocation of lipids from the organism’s soma, or bodily cells, to its germline, or reproductive system, the team claims.

Once there, the fats fuel the development of oocytes, or egg cells, making successful reproduction easier. However, the animal itself faces a higher likelihood of a shortened lifespan, the study says. When the organism again obtains nutrients, the presence of omega-3 and omega-6 fatty acids stop the travel of fats into the reproductive cells, bringing the animal’s ability to resist environmental stressors back to normal.

“SKN-1 plays essential roles in survival to stress at all stages in life; however, SKN-1 activation mutants are not long-lived. This is incredibly surprising and confusing at the same time since these animals should be stress-resistant,” said Sean Curran, an assistant professor with joint appointments at the USC Davis School of Gerontology and the USC Dornsife College of Letters, Arts and Sciences. 

The study shows that active SKN-1 doesn’t confer longevity because of the movement of lipids from the soma to the germline, which promotes the necessity of reproduction.

In the study published in the Proceedings of the National Academy of Sciences, the researchers looked at stored fat molecules within the worms visually by staining cells and biochemically with gas chromatography and mass spectrometry. The animals underwent stress from starvation and calorie restriction as well as oxidative stress from hydrogen peroxide exposure.

Oxidative stresses, which refer to an overload of reactive oxygen molecules that have been associated with cancer, can also trigger the activation of SKN-1. Since all organisms that require oxygen have to respond to oxidative stress, an understanding of how oxidative stress responses impact reproduction and vice versa is likely to yield more insights into how survival and reproduction balance against each other depending on resource availability, Curran said.

“This is particularly important in the wild, where resource availability is highly variable, and unlike in the laboratory, animals in nature must constantly assess possible risk and future reward,” he explained.

Since everything that regulates SKN-1 in worms that his team found has also been identified in humans and the balance of somatic resistance and reproduction is important for all organisms, the findings could have implications on reproductive success in older humans, Curran concluded.

In a July 2014 article that appeared in National Geographic, another maternal trait of animals has been studied by scientists. Female octopus, according to report, marks the beginning of the end as soon as it lays eggs. The mother octopus covers the eggs, defends them against would-be predators and wafts currents over them so they get a constant supply of fresh, oxygenated water. As these have to be done continuously for 53 months, the mother octopus never leaves the eggs, not even for eating. When the eggs hatch, the mother octopus dies of starvation and exhaustion. 

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